1. Field of the Invention
The present invention relates to a data file system that allows plural clients to share a data file and access the data file simultaneously, and a data access node, a brain node, a data access program storage medium that stores a data access program and a brain program storage medium that stores a brain program, which are included in the data file system.
2. Description of the Related Art
Conventionally, simultaneous data sharing type data file systems, which allow plural clients to share a data file and access the data file simultaneously, have been known. As an example of such data file systems, there is proposed a network file sharing system that performs file processing by assigning file access requests from the clients to their respective dedicated processors and returns the results to the clients, thereby avoiding performance degradation of the file server even if the number of clients increases (see patent reference 1).
Besides, there is proposed a technique that provides a server with a virtual file system which receives file access requests from the clients, thereby facilitating file management involving a system modification or file transport required due to addition of another server or the like (see patent reference 2).
Furthermore, there is proposed a technique that avoids concentration of accesses to a particular file server by a master file server receiving file access requests from the clients and assigning the requests to a file server loaded lightly (see patent reference 3).
Furthermore, there is proposed a technique that involves plural terminals which make processing requests, plural servers which carry out the processing requests and a master computer which assigns the processing requests to the respective servers, in which a server loaded lightly informs the master computer of its lightly loaded condition, and the master computer determines to which server the next processing is assigned based on the information (see patent reference 4).
Patent reference 1: Japanese Patent Laid-Open No. 5-101018
Patent reference 2: Japanese Patent Laid-Open No. 5-241934
Patent reference 3: Japanese Patent Laid-Open No. 6-332782
Patent reference 4: Japanese Patent Laid-Open No. 6-348663
Conventional simultaneous data sharing type data file systems have the problems described below. Now, the problems will be described with reference to FIG. 12.
FIG. 12 shows a configuration of a conventional simultaneous data sharing type data file system.
A data file system 3 shown in FIG. 12 has network attached storage (NAS) clients 1300 and 1400 connected to a communication line 1600 of a local area network (LAN) and a computer 1000.
The NAS clients 1300 and 1400 are computers that perform data transfer using the network file system (NFS) protocol used with UNIX (registered trademark), the common internet file system (CIFS) protocol used with Windows (registered trademark) or the like.
The computer 1000 has an MDS (Meta Data Server) node 1100, an NFS server 1200 and a disk device 1500. The disk device 1500 has a hard disk 1501 that stores metadata 1501a and a hard disk 1502 that stores data 1502a constituting a data file. The meta data 1501a is data describing information about the data file (file name, address, size, update history or the like).
In the MDS node 1100, a server application that manages data (referred to as a data management application) runs. Besides, the NFS server 1200 is a software server in which a server application for accessing data (referred to as a data access application) runs. In the NFS server 1200, data transfer is conducted according to the NFS protocol.
In the data file system 3 thus configured, the NAS client 1300 accesses a data file composed of data stored in the hard disk 1502 in the following manner, for example.
First, the NAS client 1300 sends an access request a to access the data file to the NFS server 1200.
Upon receiving the access request a, the NFS server 1200 sends an acquisition request b to acquire a file attribute, a lock or the like to the MDS node 1100. Here, the “lock” is the right to use a file, which enables a user to inhibit another user from using the file the user uses at that time.
In response to the acquisition request b, the MDS node 1100 accesses the metadata 1501a and transmits data c describing the file attribute or the like to the NFS server 1200.
Based on the data c transmitted from the MDS node 1100, the NFS server 1200 reads the data in the data 1502a stored in the hard disk 1502 via a path d and transmits the read data to the NAS client 1300 as a data file e. In this way, the data file e designated by the access request a is transferred to the NAS client 1300 that had made the access request a.
In the conventional simultaneous data sharing type data file system 3 described above, however, the data management application and the data access application run simultaneously on one computer 1000. Therefore, the conventional simultaneous data sharing type data file system is inferior in normal access performance to file systems not allowing simultaneous data sharing, which are currently widely used.
In the example described with reference to FIG. 12, one NFS server 1200 is provided. However, in general, conventional simultaneous data sharing type data file systems have plural NFS servers besides the NFS server 1200. Therefore, the MDS node 1100, at which access requests from the plural NFS servers are concentrated, has to conduct arbitration among the servers and, thus, is highly burdened. In addition, the data accesses from the plural NFS servers and CIFS servers are concentrated at the hard disk 1502. Thus, there is a problem that the whole system is degraded in access performance, and it is difficult to increase the scale (scalability) of the system.
Furthermore, if a CIFS server is provided besides the NFS server 1200, arbitration among the servers has to be conducted taking into consideration the difference in protocol between the servers, and thus, there is a problem that the processing mechanism is complicated.
Furthermore, if the disk device is expanded to accommodate more data files, the disk device configuration set in the servers has to be modified. Furthermore, if a bulk disk device is connected to the system, the data accesses from the servers are concentrated at the disk device, resulting in degraded access performance. Thus, there is a problem that it is difficult to connect a bulk disk device to the system.
As described above, in the conventional data file system 3, the computer 1000 is relatively highly burdened, which is a bottle neck that inhibits enhancement of processing speed and network communication speed in the data file system.